Buying and selling a property with Japanese knotweed: the definitive guide

Environet is the UK’s specialist in Japanese knotweed solutions for residential property owners. Our team have helped hundreds of people to buy, sell and remortgage properties affected by knotweed

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Quick facts

Awareness of knotweed is higher now than ever before, but there are many misconceptions printed in the press, resulting in the whole knotweed situation seeming like it’s a nightmare. These horror stories online can make it seem like it is almost impossible to treat, as well as being extortionately expensive. Sellers need to ensure they understand what Japanese knotweed is and how it can be treated. Once a management plan, protected by an insurance backed guarantee, has commenced by a reputable company, mortgage providers will lend because the risk has been mitigated.

Who is responsible for knotweed?

  • As an owner of private property, you are responsible for Japanese knotweed growing within the confines of your boundary. You are also advised not to allow it to spread, as you could face legal action from neighbours, or even criminal prosecution.
  • Japanese knotweed is not a notifiable weed, nor is it illegal to have it growing on your property as long you don’t allow it to spread onto adjoining land.
knotweed on neighbouring property
knotweed on housing estate

Do estate agents have to tell you about Japanese knotweed?

  • The presence of Japanese knotweed on a property is specifically classed as a “material fact”, under Regulation 5 of the Consumer Protection from Unfair Trading Regulations 2008, meaning there is a legal requirement on estate agents to make prospective buyers aware of Japanese knotweed.
  • Estate agents are not responsible for looking for or identifying Japanese knotweed on a property.
  • We believe that all estate agents should be able to recognise Japanese knotweed and provide sound advice to their clients. Early detection and treatment, including an Insurance Backed Guarantee will reduce the chance of a sale falling through.

How to buy a house with Japanese knotweed

There are many horror stories in the press and on the web which tend to overstate the reality. However, you should treat this highly invasive plant with the respect it deserves – it frequently wins the battle against DIY amateur attempts. That said, if this is the house of your dreams, don’t let the knotweed make it a nightmare. If treated correctly, Japanese knotweed can be managed, leaving you to enjoy your house for years to come. Here are our top 5 tips;

  1. Identify the scale of the problem. Get the knotweed identified by a professional as there are many plants that are often mistaken for Japanese knotweed. You can send us any pictures of the suspect plant and we will identify it free of charge.
  2. Understand the liabilities that you’ll be taking on. Make sure you understand the liabilities the knotweed presents, because it will be your responsibility as the new owner. Encroachment can be a big issue as knotweed does not respect boundaries when it grows. Has the knotweed encroached onto your land from another property? Or did the knotweed originate on your land and spread outwards? If there is a case for encroachment, then the first discussion you have with your new neighbours may not be as friendly as you had hoped.
  3. Think about potential damage. If the knotweed is growing close to the property, it may have caused damage to the building. This may not be immediately obvious, but knotweed can cause damage especially to underground structures like drains. The extensive underground system can spread much further than what you see above ground. A site survey is recommended to ensure the full extent of knotweed is identified. This survey will also try to determine where the knotweed originated from, an important fact if you are facing an encroachment claim.
  4. Consider your mortgage requirements. Perhaps most importantly you could have difficulties securing a mortgage on a property with knotweed. Some lenders reject outright any property affected by knotweed. Others take a more pragmatic view and lend where the knotweed is being removed by a reputable firm. A knotweed insurance backed guarantees will also usually needed. Speak to your mortgage provider to see what type of guarantee they require. Some ask for a 5-year guarantee and others ask for a 10-year. Make sure you understand what your mortgage provider requires before speaking with a knotweed removal company, as this will ensure you gain the correct level of coverage required.
  5. Stay involved. Don’t fall into the trap of letting the seller sort out the knotweed problem. On too many occasions we see a cheap attempt at removal with inadequate guarantees. Insist it is carried out by a firm that you trust will do the job properly and will be accepted by your mortgage provider – otherwise walk away. If the work has been carried out already, ask to see all of the documentation available and get it checked by a reputable professional.
Should you buy a house with Japanese knotweed next door? 
Buying a property with Japanese knotweed next door should not be a deal breaker, especially if you’ve found your dream house! We understand that spotting Japanese knotweed in your potential new neighbour’s garden can be worrying, but it’s crucial to address the situation responsibly and amicably. Open communication, education, and professional guidance are key to resolving the issue while maintaining a positive relationship with your neighbour. By taking these steps, you can help prevent the further spread of Japanese knotweed, and minimise its overall impact. Find out more about all the steps you should take in this situation here.
Japanese Knotweed in a garden flowerbed
A picture of Japanese knotweed

Has your seller lied about Japanese knotweed?

If you believe a seller has lied about the presence of Japanese knotweed on a property you have bought, it can place you in a difficult position. However, there are several steps you can take to reach a resolution:

  1. Document the evidence: Collect evidence to support your claim. Take photographs or videos of the suspected Japanese knotweed on the property and gather any written communication where the seller denied its presence.
  2. Check legal disclosures: Review any legal disclosures or documents provided during the property sale process, such as a TA6 form. If the seller was required to disclose the presence of Japanese knotweed and failed to do so, it could strengthen your case.
  3. Seek legal advice: Seeking legal advice from a qualified professional, such as a Conveyancer, can help guide you on the specific laws and regulations surrounding property sale, as well as your specific rights as a buyer.
  4. Contact the seller: Inform the seller about your discovery and present the evidence. It’s possible that they may not have been aware of the Japanese knotweed, or there could be a misunderstanding. Communicate your concerns and request a resolution.
  5. Try and come to a resolution with the seller: Depending on the severity of the situation, negotiate with the seller for a resolution. This could involve a reduction in the property price, removal of the knotweed, or other agreed-upon measures. If negotiations are unsuccessful, you may need to consider legal action.
  6. Consider legal action: If all previous attempts to reach a resolution with the seller have failed, you may need to take legal action against the seller for misrepresentation. Consulting legal professionals will help guide you through the legal process, whilst receiving tailored advice based on your circumstances.

How can I protect myself from knotweed risk when buying a new build home?

Residential developers are not usually required to complete the Law Society’s Property Information Form (TA6) as part of the conveyancing process, which asks a direct question about whether the property you are purchasing is affected by knotweed. But it’s in every buyer’s interest to establish if the land was treated for knotweed prior to, or during construction works. So unless your solicitor asks the question as part of their additional enquiries, it’s quite possible that you would not know if the land was affected by knotweed and whether it was professionally treated with the benefit of an insurance-backed guarantee.

  1. Insist that your solicitor gets written confirmation from the seller about whether the land was affected by knotweed.
  2. If it was, request evidence of a professional treatment plan and a ten-year insurance-backed guarantee which you can pass on to your lender.
  3. If the residential developer is unable to provide reassurances that the land is knotweed-free, commission a survey to check. 
  4. If the developer states that the property is not affected by knotweed, and it later regrows, you could have grounds for a legal claim against them.
By mid-May, established stands of Japanese knotweed are hard to miss

Do surveyors check for Japanese knotweed?

Residential surveyors have a duty of care to both the homebuyer and the mortgage lender to identify Japanese knotweed during a survey, even if the seller has attempted to hide it. While they aren’t expected to dig up the ground, vigilance is required, along with a good awareness of the various methods of concealment to ensure they don’t find themselves being sued for negligence further down the line.

  • RICS members are expected to follow the RICS Guidance Note: Japanese knotweed and residential property (23 March 2022) which lays out a framework for assessing damage and amenity impact to a property.
  • Within the Guidance, Chartered Surveyors are expected to make due enquiry relating to Japanese knotweed including:
    • a desktop study,
    • their own knowledge of the area,
    • pre-inspection checks,
    • questioning the vendor and
    • a visual inspection of the property, including all areas within 3m of the boundary.
  • Where a surveyor makes no mention of inspection for Japanese knotweed in their report or places the burden of further enquiry on the purchaser, a knotweed professional should be employed to assess the property, and/or an indemnity policy considered.
Property Surveyor checking for Japanese Knotweed
knotweed indentification

As an Estate Agent, how do I sell a property affected by knotweed?

Japanese knotweed is specifically classed as a “material fact” under the Consumer Protection Regulations (CPR), meaning there is a legal requirement on Estate Agents to make prospective buyers aware of the knotweed. We work with many estate agents, NAEA and the Guild of Estate Agents to help in the buying/selling process of knotweed affected property.

Japanese knotweed does not have to be a deal breaker. Advise any client attempting to sell a knotweed affected property to take pro-active steps to get professional treatment underway before the buyer is taken by surprise at the 11th hour, risking the sale. It’s important the seller discloses the presence of knotweed in order to avoid being sued for misrepresentation down the line.

  1. Familiarise yourself with what this highly invasive plant looks like.
  2. Keep your knowledge up to date by attending one of our webinars.
  3. Proactively ask your clients about knotweed during your valuation.
  4. Reassure your clients that with the right expert on board, knotweed need not be a problem.

Will a homebuyers survey pick up Japanese knotweed?

The level of inspection required does depend on the type of survey that has been commissioned. All surveys, including a homebuyers report require the surveyor to “carry out a visual inspection of the grounds from within the boundaries of the subject property, and, where necessary, from adjoining public property” (RICS Home survey standard, 2019).

  • During a Level 2 Homebuyers Survey, surveyors are expected to perform a thorough inspection of the grounds, noting any limitations.
  • The measure of adequacy of any individual inspection remains the long-established one of ‘reasonableness’, which is largely determined by the particular circumstances facing the surveyor on the day of the inspection.
  • There are many reasons why a completely competent inspection might not identify the presence of Japanese knotweed at a property.
homebuyers survey being conducted - looking for Japanese Knotweed
Japanese knotweed crowns during a residential dig out in Bath

What to do if your surveyor fails to spot Japanese knotweed?

What happens if a surveyor misses Japanese knotweed growing on a property you wish to buy?

Sellers have a legal obligation to declare if a property is affected by knotweed when they sell. However, some will claim they aren’t aware of it “to the best of their knowledge”, while others will attempt to conceal the weed by cutting it back, burning it, covering it with lawn or chippings, in the hope it isn’t discovered, particularly during late autumn and winter when the plant dies back. 

This means a surveyor is often a buyer’s last line of defence. But what happens if they miss Japanese knotweed growing on a property you wish to  buy?

Surveyors have a duty of care to both the homebuyer and the lender to identify Japanese knotweed during a survey, even if the seller has attempted to hide it. While they aren’t expected to dig up the ground, extra vigilance is required, along with a good awareness of the various methods of concealment to ensure they don’t find themselves being sued for negligence further down the line. 

If there is any doubt at all, the surveyor should recommend further investigation or suggest that the buyer takes out an inexpensive Japanese knotweed indemnity policy that will cover the cost of treatment, repairs, legal costs for third party claims and any proven diminution in their property when it is sold.

If a surveyor fails to identify knotweed during a survey, the buyer may have a claim against them if professional negligence can be proved.

Need help? Get in touch. 

Is it worth buying a house with Japanese knotweed?

If you’re asking yourself this question, then you’re not alone. Research completed by Environet through YouGov in 2019 revealed that more than 50% of people would be put off buying a house affected by Japanese knotweed. The same survey revealed that almost a third (32%) of British adults who are aware of the invasive plant say they would be prepared to go ahead and buy an affected property, as long as they could negotiate an appropriate discount on the price. If you are not immediately running for the hills at the prospect of buying a property affected by knotweed, remember the following.

  • Always do your research, and complete your due diligence checks before proceeding.
  • Speak to an expert and get an impartial opinion on the property and any management plan that has been implemented, including the guarantee offer.
  • Where a plan is already in place, speak to the provider and make sure you are happy with them as a service provider – you may need to maintain a relationship with them for a number of years!


Having completed all of the above checks, and also followed our top tips for buyers, then you may find that elusive dream property is still within reach!

a house with Japanese knotweed
calculator and paperwork image

Can I get a mortgage with Japanese knotweed?

Most mortgage lenders including building societies and high street banks will refuse to lend money in the form of a mortgage where their surveyor identifies the presence of Japanese knotweed on the property until a suitable Management Plan is in place. Refusal has also resulted where no Japanese knotweed is present on the site, but is on adjoining land, although an update to the RICS Guidance published in 2022 will make this less likely in future. Unfortunately there is not a hard and fast rule, as it is usually dealt with on a case by case basis. Some lenders will outright refuse to lend on properties affected by knotweed though, so it is always worth checking their policies as soon as possible.

  • Banks refuse mortgages because Japanese knotweed can cause property damage or a loss in amenity value which, in turn can devalue the property. This affects the loan to value ratio and reduces the value of the security held by the bank. Lending money on a property with untreated knotweed is often a risk the banks are not willing to take.
  • The key to obtaining lending on a Japanese knotweed affected property is having a Japanese knotweed management plan in place, supported by an insurance backed guarantee, for either 5 or 10 years. This is usually enough to ensure that the sale of a property can go through without a hitch, though the lender may specify that the knotweed treatment or removal plan has either been completed prior to exchange, or that the costs have been paid for and the work scheduled in.
  • Learn more about Japanese knotweed and mortgages here.

What to do if a mortgage is refused due to Japanese Knotweed?

Firstly, don’t panic. Most Building societies and mortgage lenders impose strict lending criteria on residential properties known to be affected by Japanese knotweed. Lending policies vary wildly from lender to lender, meaning there is usually a solution to the problem.

  • Most lenders publish their lending criteria online, so a quick web search for the key words of the “lender name” and “Japanese knotweed policy” should reveal what it is you’ll need to do to satisfy their requirements. Some lenders may specify that the knotweed treatment or removal plan must be completed prior to exchange, or that the costs have been paid for and the work scheduled in.
  • Once you know what you need, you can go back to the vendor and negotiate.
  • If the vendor is unwilling, or unable to accommodate the criteria of your first-choice lender, but you are satisfied with the proposed knotweed management plan, then ask your broker to shop around. You may be able to find an alternative lender – although you should carefully consider any cost implication of signing up to an alternative deal, versus the cost of dealing with the knotweed problem upfront.
  • Learn more about Japanese knotweed and mortgages here 

Can you sell your house if you have Japanese knotweed?

It is true, many sales have fallen through as a result of Japanese knotweed but more often than not, it is as a result of mismanagement or poor communication rather than the knotweed itself. Japanese knotweed should not prevent a house sale being completed; it just adds a few steps into the process. Once the knotweed is controlled, with a suitable insurance backed guarantee, mortgage providers and sellers will be more inclined to proceed.

Unfortunately, the presence of Japanese knotweed on a property often means that you will achieve a lower value for your property than you might have hoped. That being said, all is not lost. Follow our Top Tips for Sellers below to maximise your chances of a smooth transaction and preserving the value of your property.

How to sell a house with Japanese knotweed?

A property with Japanese knotweed on the land can make for a difficult sale. Buyers would much prefer to buy a knotweed-free property because it is one less thing for them to worry about. This is where you as the seller need to make the most out of the situation, in order to make your property attractive to potential buyers. If you can provide the prospective with all the information they need, it will help to ensure that the knotweed issue isn’t blown out of proportion. Here are our top tips:

  • Don’t stick your head in the sand! Concealment or hoping that nobody will notice the knotweed is no way to go about pushing the sale of your house through. Firstly, Chartered Surveyors are trained to spot knotweed, and are obliged to report its presence either on your property or within 3m of your boundary. Secondly, you are actually breaking the law. The Law Society’s TA6 form has a specific question relating to Japanese knotweed and if answered untruthfully during the conveyancing process a legal claim of misrepresentation could be brought against you by the buyer down the line.
  • Do it the right way the first time. You should look to commission a reputable Japanese knotweed removal firm to remove the knotweed and provide suitable guarantees. Don’t fall into the trap of applying home remedies to Japanese knotweed – any DIY attempts will not be supported by banks.
  • Get an expert on board you can trust. You should instruct a Japanese knotweed removal firm that you have confidence in to guide you through the entire process, including sound consultancy, great customer service and a willingness to engage with all parties involved.
  • Choose the right method and secure the right guarantees. When you are selling your property, you need to consider the requirements of any potential purchaser. It is tempting to choose the cheapest option and hope for the best – but in our experience buyers are quick to pull out where a robust management plan is absent. Also ensure that any work you instruct comes with a decent insurance backed guarantee that will be fully transferable to the new owner and accepted by all of the major lenders.
  • Take the advice of experts. Don’t be afraid to ask questions before you settle on a solution. Rest assured that the knotweed problem is resolved, and potential buyers and lenders should find no reason to worry about the knotweed, allowing for a smooth sales transaction.
japanese knotweed behind a shed

How much does Japanese knotweed Devalue your Home?

How does Japanese knotweed affect Property Value?

Where Japanese knotweed is identified on a property, the value is often negatively affected. Typically, affected properties are worth around 3-15% less than their unaffected counterparts for the following reasons:

  • A mortgage provider will often place restrictions on lending. Policies vary, from zero tolerance to stipulations such as the requirement for an Insurance Backed Guarantee to be in place, or a treatment programme completed. These restrictions can limit the ability of a buyer to secure lending.
  • The cost of treatment or removal of the problem will directly affect the value of a property.
  • ‘Knotweed stigma’ will deter some buyers, even if the knotweed is removed, and is likely to make a property less appealing, resulting in fewer, and lower offers.
  • Residual loss of amenity value and/or restrictions on future use will also impact on value. It is for this reason that we developed JK VIM, to highlight the likely differences in the value of their asset, based on the treatment and guarantee options they choose to employ.
  • It is important to note that in most cases, the diminution in value caused by Japanese knotweed can be dramatically reduced through sound consultancy from a reputable Japanese knotweed expert.

How to stop Japanese knotweed encroaching onto your land

Japanese knotweed is not fussy about where it grows, which is demonstrated in our gallery of knotweed pictures. It has an uncanny desire to grow along and across property boundaries, without any respect for them. It spreads its invasive rhizomes and continues to encroach and wreak havoc until action is taken against it.

  • The damage Japanese knotweed can cause should not be under-estimated, so if you notice Japanese knotweed encroaching onto your land, you should take immediate action.
  • Notify the adjoining landowner of the problem, preferably in writing. A co-ordinated approach that tackles the Japanese knotweed on both pieces of land is much more likely to be successful than piecemeal attempts.
  • Talk to us about a Treatment Plan and try to agree with the adjoining landowner the allocation of costs. We have a number of different Japanese knotweed removal methods we can use, to ensure that the knotweed is completely removed. If required, Guarantees can be issued to both properties once the work has been completed.
  • If you can’t agree a way forward with the adjoining owner, (some are more receptive and motivated than others) then your options are to look for a Japanese knotweed control method, such as using herbicides and or vertical root barriers or to seek legal redress.
Japanese knotweed on neighbours land
Huge clump of Knotweed - council unlikley to help remove it

Will the Council help with Japanese knotweed?

Local councils have no responsibility for Japanese knotweed located on private property and are therefore unlikely to be able to help with a knotweed problem. Where Japanese knotweed is growing on Council-owned land, they have a duty of care as any landowner does to prevent it spreading into the wild, encroaching on to adjoining land or generally causing a nuisance.

  • Some councils have a fund to help residents with Japanese knotweed treatment, but this is the exception rather than the rule. It is also very unlikely that any funding would stretch to a professional treatment plan with an insurance backed guarantee.
  • Councils have legislation at their disposal aimed at preventing unreasonable behaviour that is having a negative impact on the local community’s quality of life. Where a landowner fails to act on their knotweed problem, the local council may be prepared to issue them with a warning followed by a Community Protection Notice. This would force them to deal with the knotweed or face a criminal prosecution.

Start fixing your invasive plant problem today by requesting a survey

Rest assured, where invasive species are identified at an early stage and tackled correctly, problems can usually be avoided. Our specialist consultants complete thorough surveys to identify the extent of the problem. Our plans aren’t one-size-fits-all; they’re customised to tackle the invasive species at your property effectively, taking account of all of your requirements. 

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